Field of the Invention
The present invention relates to an image forming system, an image forming apparatus, and an image formation control program. In particular, the present invention relates to a technique at the time of executing image formation of another image in the middle of executing image formation by using long sheets, such as a continuous sheet and a rolled sheet.
Description of Related Art
In image forming apparatuses, such as a printer which performs image formation based on image data, it is common to form images onto a sheet called a cut sheet which is cut out into a predetermined fixed sheet size, such as a letter size.
On the other hand, in such an image forming apparatus, it is also possible to form images onto a long sheet called a continuous sheet or a rolled sheet with a sheet length longer in a conveying direction than a sheet with a fixed size. Such a long sheet is used for use purposes, for example, printing repeatedly a label with a seal format, such as an address, a serial number, and a commodity indication.
In such an image forming apparatus, in order to maintain the density, color, position, etc. of an image to be formed to a proper state, correction is executed for the density, color, position, etc. of an image to be formed for every predetermined period. In this case, an image for adjustment (adjustment chart) is formed by using adjustment image data other than ordinary image data, and then this adjustment chart is read by a sensor. Subsequently, based on the read result of the adjustment chart, correction is executed for the density, color, and position of an image to be formed.
Herein, there exists also a technique of not transferring an adjustment chart onto a sheet by reading it by a sensor in the state that an image of the adjustment chart is formed on a photoreceptor. However, by reading an adjustment chart transferred onto a sheet actually, it becomes possible to perform measurement much more correctly.
In the case where an adjustment chart is transferred onto a cut sheet of a fixed sheet size, only a sheet onto which image formation of an adjustment image is executed during image formation of ordinary images, is removed from ordinary sheets. Thereby, any problem does not occur in output resultant matters (a group of sheets subjected to image formation of ordinary images).
However, in the case of an image forming apparatus which executes sheet feeding, image formation, and sheet delivering (winding up a long sheet without any change) by using a long sheet, situations become different. That is, a problem arises in that an adjustment chart mixes into output resultant matters made by using the long sheet. However, if adjustment for an image density and an image position by using an adjustment image is not executed for each time after a predetermined amount of image formation has been executed, there may be a possibility that a desired image quality cannot be maintained.